In the older processes and apparatus, the liquid electrolyte was conducted through the multi-cell electrolytic tank in such a way that uniform precipitation on the electrodes did not occur. This irregular precipitation results if the liquid distribution in the tank is not absolutely uniform.
In electrolysis installations possessing a plurality of anode and cathode plates connected electrically one behind the other in a common tank, uniform supply to and flow through, the individual cells is of greatest importance. Due to the uniform precipitation of e.g. copper from the liquid electrolyte on the electrodes, the precipitated copper can then immediately be used again in the etching process. Therefore, a recycling process is achieved, among other things.
In one of these known devices the sensor was located in the etching fluid, which is circulated continuously. Even if one places the sensor into stagnating areas of the etching tank, the measured result is still so imprecise that the purpose of the invention, namely to obtain an optimum etching rate, is not achieved. By immersion of circuit boards into the etching fluid, its physical and chemical composition changes. It has been found that to get an optimum etching rate, certain parameters of the chemical and/or physical constitution of the etching fluid must exist.
The present process relates to ecophile etching, i.e. the etching fluid is circulated continuously. It is not exchanged, as in known processes, when it is used up, but is regenerated or is given additions which ensure that an optimum etching rate exists.